1. Mobile needs to have somewhat spacious UIs to deal with touch targets needing to be finger sized.

2. Companies don't want to design two very different UIs and by-in-large users prefer their skills transfer across platforms.

3. Accessibility is easier if the design leaves room for bigger font sizes and doesn't require fine motor control. Watching my dad start to noticeably age I'm realizing that even spacious spacious apps don't go far enough in this regard.

I'm not sure how we get to information dense design without something changing the forces that pushed us that way in the first place.